Today we tried to configure a PTP 650 link for 5.4Ghz. The link is only 2.9km long and we are using 2ft Dial polarity 29dbi dishes. The installation wizard would not allow us more than 2dBm max receive power. The link is in the US but we have PTP 500 running in the same band at 5dbm?
Any help or knowledge would be appreciated!
Hi Tom
I would recomend that you download our free LINKPlanner tool which will help you plan your links - The installation report will confirm that the Max Transmit power is 2dB (I’ll explain below)
You can download LINKPlanner from
https://support.cambiumnetworks.com/files/linkplanner
The FCC regulations give a max EIRP of 30dBm. This takes into account the antenna - so in your case
Antenna Gain - 29dBi
Cable Loss - 1dB
30 -29 + 1 = 2
So - The max power allowed by regulation is 2dB
If you had a smaller antenna, such as our integrated 23dBi antenna, then the unit would allow you to use higher Tx power (with a 23dBi integrated antenna you will be allowed 7dB max transmit power - 30-23+0 - The zero is because there is zero cable loss in an integrated unit)
The EiRP regulations do change by bandwidth, There is a EIRP density limit - so at the smaller bandwidths - 5MHz - you will be allowed 24dBm
For a small Line of Sight link this does not matter - infact, although these are the max Tx values by regulation, you will not want to be running your link at these powers, as you would be blasting the reciever. The PTP650 does have automatic transmit power control, so will adjust the power down to a suitable level.
The larger antennas would only be of benefit if the link is a non-line of sight link.
Rather than looking at the Tx power, I would be looking to ensure that my Rx power matches the prediction in LINKPlanner, to ensure that allignment is correct, and looking at the throughput that the radio is achieving
Regards
What are the “reciever blasting thresholds”, for cambium epmp gear? (in db)